Nanostructures such as carbon nanofibers, cabon nanotubes, carbon nanohorns and nanowires containing Si, Ge, an alloy of III and V-group elements (e.g., GaAs, GaP, InAs/P) or an alloy of II and VI-group elements (e.g., ZnS, ZnSe, CdS, CdSe) have good mechanical strength, heat- and electro-conductivity and chemical stability, suitable for various industrial applications.
In particular, when used as an emission source of a field emission array in an electronic device, the nanostructure is capable of increasing the work function and lowering the driving voltage due to its high aspect ratio (=length/diameter), as compared to a conventional field emission source such as an Mo tip (see FIG. 1). Such a field emission array comprising a nanostructure field emission source can be prepared by directly growing nanostructures on a patterned electrode layer formed on a supporting plate using a chemical vapor deposition, as disclosed in Korean Patent Publication No. 2001-91389. However, the method is not suitable for the preparation of a field emission array having a large area.
In order to overcome the above problem, there has been reported a method of preparing a field emission array by screen printing on a patterned electrode layer formed on a supporting substrate a paste or slurry composition comprising carbon nanostructures in combination with an organic binder and an organic dispersing agent (Korean Patent Publication Nos. 2000-61757 and 2000-20870). A schematic diagram of a field emission array prepared by this method, which comprises a substrate/electrode layer (10) and a layer of nanostructures (30) fixed thereto by a paste medium (20), is shown in FIG. 2.
Such a screen printing method makes a preparation of a large-area field emission array possible, but has a problem in that organic materials remaining in the nanostructure layer generate undesired gases under an evacuated condition, lowering the display efficiency.
For the purpose of solving this problem, there have been reported a method of further adding into the paste or slurry composition a heat-decomposition accelerator to heat-decompose organic materials (Korean Patent Publication No. 2001-109538) and a method of applying a voltage to a mixed solution of a polymer precursor and a carbon nanostructure to carry out in situ electrochemical polymerization (Korean Patent Publication No. 2001-17543). However, these methods cannot completely eradicate the problem associated with using an organic material.